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Re: [Amps] Amplifier Vs Plate Modulated

To: Paul Baldock <>, Amps group <>
Subject: Re: [Amps] Amplifier Vs Plate Modulated
From: "Fuqua, Bill L" <>
Date: Thu, 3 Dec 2015 21:18:56 +0000
List-post: <">>
  Most all old amplifiers were spec. at 40%  carrier for AM compared to CW. 
I did say the limits were plate dissipation or PEP output, the lesser of the 
I had to go back and take a look at waveforms. With full carrier single 
sideband you 
need to keep the sideband power level to less than 50% and to keep envelope 
happy is should be 25%.
  Diode detectors if operated as ideal square law detectors introduce 
considerable distortion.
Fortunately, most AM diode detectors are operated lots of drive, thanks to IF 
amplifiers and AVC,  and the drop across the
diode is small in comparison to the output voltage. 
  Now saying that CHU uses full carrier SSB. I need to take a look at that and 
I recall many years ago that one SSB transmitter emulated AM by just injecting 
carrier with
one sideband. But I can't recall where I saw it. You have to remember those 
were the
days that there was little concern about distortion.

Bill wa4lav

From: Amps [] on behalf of Paul Baldock 
Sent: Wednesday, December 02, 2015 5:55 PM
To: Amps group
Subject: Re: [Amps] Amplifier Vs Plate Modulated

I assure you that AM is alive and well.

You might also consider that most older amps (not all) when you are
not speaking on SSB have 0% efficiency, and around 300W to 400W plate

You may have noticed that on AM many operators talk and talk and
talk. You probably thought they were just long winded. But no, they
are just trying to keep the efficiency up.

- Paul KW7Y

At 10:40 AM 12/2/2015, Bill Turner wrote:
>------------ ORIGINAL MESSAGE ------------(may be snipped)
>On Mon, 30 Nov 2015 23:34:01 -0600, Gary wrote:
> >With AM at 375 watts carrier out and no modulation, the efficiency of that
> >amp will be around 30%. That requires the input power to be 1250 watts. That
> >leaves 875 watts of plate dissipation with no modulation present.
>And this is one reason why AM has become mostly a curiosity.  :-)
>73, Bill W6WRT
>Amps mailing list

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